<h2>DESCRIPTION</h2>

<em>i.evapo.pt</em> Calculates the diurnal evapotranspiration after Prestley
and Taylor (1972). The Priestley-Taylor model (Priestley and Taylor, 1972)
is a modification of Penman's more theoretical equation.

<h2>NOTES</h2>
RNETD optional output from <em>i.evapo.potrad</em> is giving good results as input
for net radiation in this module.

<p>Alpha values:
<ul>
<li> 1.32 for estimates from vegetated areas as a result of the increase in
surface roughness (Morton, 1983; Brutsaert and Stricker, 1979)
<li> 1.26 is applicable in humid climates (De Bruin and Keijman, 1979;
Stewart and Rouse, 1976; Shuttleworth and Calder, 1979), and temperate
hardwood swamps (Munro, 1979)
<li> 1.74 has been recommended for estimating potential evapotranspiration
in more arid regions (ASCE, 1990). This worked well in Greece with University
of Thessaloniki.
</ul>

Alpha values extracted from:
<a href="http://www.civil.uwaterloo.ca/Watflood/Manual/02_03_1.htm">Watflood manual</a>.

<h2>SEE ALSO</h2>

<em>
<a href="i.evapo.mh.html">i.evapo.mh</a>,
<a href="i.evapo.pm.html">i.evapo.pm</a>,
<a href="i.evapo.time.html">i.evapo.time</a>,
<a href="i.eb.netrad.html">i.eb.netrad</a>,
<a href="r.sun.html">r.sun</a>
</em>

<h2>AUTHORS</h2>

Yann Chemin, GRASS Development Team, 2007-08

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